/*
 * $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//httpclient/src/java/org/apache/commons/httpclient/util/ParameterParser.java,v 1.5 2004/05/13 04:01:22 mbecke Exp $
 * $Revision: 480424 $
 * $Date: 2006-11-29 06:56:49 +0100 (Wed, 29 Nov 2006) $
 *
 * ====================================================================
 *
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.commons.httpclient.util;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.httpclient.NameValuePair;

/**
 * A simple parser intended to parse sequences of name/value pairs. Parameter
 * values are exptected to be enclosed in quotes if they contain unsafe
 * characters, such as '=' characters or separators. Parameter values are
 * optional and can be omitted.
 * 
 * <p>
 * <code>param1 = value; param2 = "anything goes; really"; param3</code>
 * </p>
 * 
 * @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
 * 
 * @since 3.0
 */
public class ParameterParser {

	/** String to be parsed */
	private char[] chars = null;

	/** Current position in the string */
	private int pos = 0;

	/** Maximum position in the string */
	private int len = 0;

	/** Start of a token */
	private int i1 = 0;

	/** End of a token */
	private int i2 = 0;

	/** Default ParameterParser constructor */
	public ParameterParser() {
		super();
	}

	/** Are there any characters left to parse? */
	private boolean hasChar() {
		return this.pos < this.len;
	}

	/** A helper method to process the parsed token. */
	private String getToken(boolean quoted) {
		// Trim leading white spaces
		while ((i1 < i2) && (Character.isWhitespace(chars[i1]))) {
			i1++;
		}
		// Trim trailing white spaces
		while ((i2 > i1) && (Character.isWhitespace(chars[i2 - 1]))) {
			i2--;
		}
		// Strip away quotes if necessary
		if (quoted) {
			if (((i2 - i1) >= 2) && (chars[i1] == '"')
					&& (chars[i2 - 1] == '"')) {
				i1++;
				i2--;
			}
		}
		String result = null;
		if (i2 >= i1) {
			result = new String(chars, i1, i2 - i1);
		}
		return result;
	}

	/** Is given character present in the array of characters? */
	private boolean isOneOf(char ch, char[] charray) {
		boolean result = false;
		for (int i = 0; i < charray.length; i++) {
			if (ch == charray[i]) {
				result = true;
				break;
			}
		}
		return result;
	}

	/**
	 * Parse out a token until any of the given terminators is encountered.
	 */
	private String parseToken(final char[] terminators) {
		char ch;
		i1 = pos;
		i2 = pos;
		while (hasChar()) {
			ch = chars[pos];
			if (isOneOf(ch, terminators)) {
				break;
			}
			i2++;
			pos++;
		}
		return getToken(false);
	}

	/**
	 * Parse out a token until any of the given terminators is encountered.
	 * Special characters in quoted tokens are escaped.
	 */
	private String parseQuotedToken(final char[] terminators) {
		char ch;
		i1 = pos;
		i2 = pos;
		boolean quoted = false;
		boolean charEscaped = false;
		while (hasChar()) {
			ch = chars[pos];
			if (!quoted && isOneOf(ch, terminators)) {
				break;
			}
			if (!charEscaped && ch == '"') {
				quoted = !quoted;
			}
			charEscaped = (!charEscaped && ch == '\\');
			i2++;
			pos++;

		}
		return getToken(true);
	}

	/**
	 * Extracts a list of {@link NameValuePair}s from the given string.
	 * 
	 * @param str
	 *            the string that contains a sequence of name/value pairs
	 * @return a list of {@link NameValuePair}s
	 * 
	 */
	public List parse(final String str, char separator) {

		if (str == null) {
			return new ArrayList();
		}
		return parse(str.toCharArray(), separator);
	}

	/**
	 * Extracts a list of {@link NameValuePair}s from the given array of
	 * characters.
	 * 
	 * @param chars
	 *            the array of characters that contains a sequence of name/value
	 *            pairs
	 * 
	 * @return a list of {@link NameValuePair}s
	 */
	public List parse(final char[] chars, char separator) {

		if (chars == null) {
			return new ArrayList();
		}
		return parse(chars, 0, chars.length, separator);
	}

	/**
	 * Extracts a list of {@link NameValuePair}s from the given array of
	 * characters.
	 * 
	 * @param chars
	 *            the array of characters that contains a sequence of name/value
	 *            pairs
	 * @param offset
	 *            - the initial offset.
	 * @param length
	 *            - the length.
	 * 
	 * @return a list of {@link NameValuePair}s
	 */
	public List parse(final char[] chars, int offset, int length, char separator) {

		if (chars == null) {
			return new ArrayList();
		}
		List params = new ArrayList();
		this.chars = chars;
		this.pos = offset;
		this.len = length;

		String paramName = null;
		String paramValue = null;
		while (hasChar()) {
			paramName = parseToken(new char[] { '=', separator });
			paramValue = null;
			if (hasChar() && (chars[pos] == '=')) {
				pos++; // skip '='
				paramValue = parseQuotedToken(new char[] { separator });
			}
			if (hasChar() && (chars[pos] == separator)) {
				pos++; // skip separator
			}
			if (paramName != null
					&& !(paramName.equals("") && paramValue == null)) {
				params.add(new NameValuePair(paramName, paramValue));
			}
		}
		return params;
	}
}
